U.S. patent application number 12/618306 was filed with the patent office on 2010-05-27 for image processing systems.
This patent application is currently assigned to Voyage Medical, Inc.. Invention is credited to Ted J. COOPER, Zachary J. MALCHANO, David MILLER, Ruey-Feng PEH, Vahid SAADAT, Veerappan SWAMINATHAN.
Application Number | 20100130836 12/618306 |
Document ID | / |
Family ID | 42196946 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100130836 |
Kind Code |
A1 |
MALCHANO; Zachary J. ; et
al. |
May 27, 2010 |
IMAGE PROCESSING SYSTEMS
Abstract
Image processing systems are described which utilize various
methods and processing algorithms for enhancing or facilitating
visual detection and/or sensing modalities for images captured in
vivo by an intravascular visualization and treatment catheter. Such
assemblies are configured to deliver energy, such as RF ablation,
to an underlying target tissue for treatment in a controlled manner
while directly visualizing the tissue during the ablation
process.
Inventors: |
MALCHANO; Zachary J.; (San
Francisco, CA) ; PEH; Ruey-Feng; (Mountain View,
CA) ; SAADAT; Vahid; (Atherton, CA) ; COOPER;
Ted J.; (Sunnyvale, CA) ; MILLER; David;
(Cupertino, CA) ; SWAMINATHAN; Veerappan;
(Sunnyvale, CA) |
Correspondence
Address: |
LEVINE BAGADE HAN LLP
2400 GENG ROAD, SUITE 120
PALO ALTO
CA
94303
US
|
Assignee: |
Voyage Medical, Inc.
Redwood City
CA
|
Family ID: |
42196946 |
Appl. No.: |
12/618306 |
Filed: |
November 13, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61114834 |
Nov 14, 2008 |
|
|
|
Current U.S.
Class: |
600/301 ;
600/407; 600/509 |
Current CPC
Class: |
A61B 5/366 20210101;
A61B 5/6852 20130101; A61B 5/0084 20130101; A61B 5/7289 20130101;
A61B 5/0245 20130101; A61B 5/283 20210101; A61B 2218/002 20130101;
A61B 5/7285 20130101; A61B 5/113 20130101; A61B 5/01 20130101; A61B
5/349 20210101; A61B 5/742 20130101; A61B 18/1492 20130101; A61B
5/0538 20130101; A61B 1/05 20130101 |
Class at
Publication: |
600/301 ;
600/407; 600/509 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 5/05 20060101 A61B005/05; A61B 5/0472 20060101
A61B005/0472 |
Claims
1. A method of imaging a tissue region which is under motion,
comprising: visualizing a tissue region within a body via an
intravascular imaging device; recording electrical activity of the
tissue region while visualizing the tissue region; selecting an
event which repeats at least periodically in the electrical
activity; and, coordinating a visual image of the tissue region
captured during the event to correspond to the event.
2. The method of claim 1 further comprising displaying the visual
image corresponding to the event.
3. The method of claim 1 further comprising coordinating a
plurality of visual images each captured during the event over a
plurality of repeated events.
4. The method of claim 1 wherein visualizing comprises viewing the
tissue region through an open hood in contact with the tissue
region and which is purged of blood with a fluid.
5. The method of claim 1 wherein visualizing comprises visualizing
cardiac tissue within a chamber of a heart.
6. The method of claim 1 wherein visualizing further comprises
recording the visual images of the tissue region simultaneously
while recording electrical activity.
7. The method of claim 1 wherein recording comprises recording
electrocardiogram data of the tissue region.
8. The method of claim 1 wherein selecting an event comprises
selecting an electrical event during a QRS Complex of the tissue
region.
9. The method of claim 1 wherein coordinating comprises registering
one or more ablation parameters to the event.
10. The method of claim 1 further comprising capturing one or more
additional visual images gated by the event over a period of
time.
11. The method of claim 1 wherein coordinating comprises
coordinating the visual image captured at a time delayed from the
event.
12. A method of imaging a tissue region, comprising: visualizing
one or more lesions over a tissue region within a body via an
intravascular imaging device; identifying a location of the one or
more lesions relative to one another over the tissue region; and,
visually displaying the relative locations of each of the one or
more tissue regions.
13. The method of claim 12 wherein visualizing comprises
visualizing cardiac tissue within a chamber of a heart.
14. The method of claim 12 further comprising registering ablation
parameters for each of the one or more lesions.
15. The method of claim 12 further comprising indicating a
direction of a first lesion relative to a second lesion.
16. A method of imaging a tissue region, comprising: visualizing
one or more lesions in vivo over a tissue region within a body
through an intravascular imaging device; measuring a temperature
and/or electrical potential of the one or more lesions; and
overlaying a gradient indicative of the temperature and/or
electrical potential upon a visual image of the one or more lesions
captured in vivo.
17. The method of claim 16 wherein visualizing comprises
visualizing cardiac tissue within a chamber of a heart.
18. The method of claim 16 wherein measuring comprises sensing the
temperature and/or electrical potential via one or more sensors
positioned on the imaging device.
19. The method of claim 16 wherein overlaying comprises imaging the
one or more lesions during an ablation procedure.
20. The method of claim 16 further comprising displaying the
gradient superimposed upon the visual image.
21. The method of claim 20 wherein displaying comprises displaying
one or more visual images of the one or more lesions captured
incrementally over time during an ablation procedure.
22. A method of imaging a tissue region, comprising: visualizing
one or more lesions in vivo over a tissue region within a body
through an intravascular imaging device; recording a color
histogram of the one or more lesions during an ablation procedure;
monitoring a rate of change of the color histogram during the
ablation procedure; and, detecting an appearance of a color
indicative of ablation completion of the one or more lesions.
23. The method of claim 22 wherein visualizing comprises
visualizing cardiac tissue within a chamber of a heart.
24. The method of claim 22 wherein monitoring a rate of change
further comprises monitoring a surface reflectance of the one or
more lesions.
25. The method of claim 22 wherein detecting an appearance
comprises detecting for the appearance of a white, brown, yellow,
or black color upon the one or more lesions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Prov. Pat. App. 61/114,834 filed Nov. 14, 2008, which is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to medical devices
used for visualizing and/or assessing regions of tissue within a
body. More particularly, the present invention relates to methods
and apparatus for visualizing and/or assessing regions of tissue
within a body, such as the chambers of a heart, to facilitate
diagnoses and/or treatments for the tissue.
BACKGROUND OF THE INVENTION
[0003] Conventional devices for visualizing interior regions of a
body lumen are known. For example, ultrasound devices have been
used to produce images from within a body in vivo. Ultrasound has
been used both with and without contrast agents, which typically
enhance ultrasound-derived images.
[0004] Other conventional methods have utilized catheters or probes
having position sensors deployed within the body lumen, such as the
interior of a cardiac chamber. These types of positional sensors
are typically used to determine the movement of a cardiac tissue
surface or the electrical activity within the cardiac tissue. When
a sufficient number of points have been sampled by the sensors, a
"map" of the cardiac tissue may be generated.
[0005] Another conventional device utilizes an inflatable balloon
which is typically introduced intravascularly in a deflated state
and then inflated against the tissue region to be examined. Imaging
is typically accomplished by an optical fiber or other apparatus
such as electronic chips for viewing the tissue through the
membrane(s) of the inflated balloon. Moreover, the balloon must
generally be inflated for imaging. Other conventional balloons
utilize a cavity or depression formed at a distal end of the
inflated balloon. This cavity or depression is pressed against the
tissue to be examined and is flushed with a clear fluid to provide
a clear pathway through the blood.
[0006] However, such imaging balloons have many inherent
disadvantages. For instance, such balloons generally require that
the balloon be inflated to a relatively large size which may
undesirably displace surrounding tissue and interfere with fine
positioning of the imaging system against the tissue. Moreover, the
working area created by such inflatable balloons are generally
cramped and limited in size. Furthermore, inflated balloons may be
susceptible to pressure changes in the surrounding fluid. For
example, if the environment surrounding the inflated balloon
undergoes pressure changes, e.g., during systolic and diastolic
pressure cycles in a beating heart, the constant pressure change
may affect the inflated balloon volume and its positioning to
produce unsteady or undesirable conditions for optimal tissue
imaging. Additionally, imaging balloons are subject to producing
poor or blurred tissue images if the balloon is not firmly pressed
against the tissue surface because of intervening blood between the
balloon and tissue.
[0007] Accordingly, these types of imaging modalities are generally
unable to provide desirable images useful for sufficient diagnosis
and therapy of the endoluminal structure, due in part to factors
such as dynamic forces generated by the natural movement of the
heart. Moreover, anatomic structures within the body can occlude or
obstruct the image acquisition process. Also, the presence and
movement of opaque bodily fluids such as blood generally make in
vivo imaging of tissue regions within the heart difficult.
Moreover, once a visual image of a tissue region is acquired in
vivo, there may be additional difficulties in assessing the
condition of the underlying tissue for appropriate treatments or
treatment parameters.
[0008] Thus, a tissue imaging system which is able to provide
real-time in vivo images and assessments of tissue regions within
body lumens such as the heart through opaque media such as blood
and which also provide instruments for therapeutic procedures upon
the visualized tissue are desirable.
SUMMARY OF THE INVENTION
[0009] In describing the tissue imaging and manipulation apparatus
that may be utilized for procedures within a body lumen, such as
the heart, in which visualization of the surrounding tissue is made
difficult, if not impossible, by medium contained within the lumen
such as blood, is described below. Generally, such a tissue imaging
and manipulation apparatus comprises an optional delivery catheter
or sheath through which a deployment catheter and imaging hood may
be advanced for placement against or adjacent to the tissue to be
imaged.
[0010] The deployment catheter may define a fluid delivery lumen
therethrough as well as an imaging lumen within which an optical
imaging fiber or assembly may be disposed for imaging tissue. When
deployed, the imaging hood may be expanded into any number of
shapes, e.g., cylindrical, conical as shown, semi-spherical, etc.,
provided that an open area or field is defined by the imaging hood.
The open area is the area within which the tissue region of
interest may be imaged. The imaging hood may also define an
atraumatic contact lip or edge for placement or abutment against
the tissue region of interest. Moreover, the distal end of the
deployment catheter or separate manipulatable catheters may be
articulated through various controlling mechanisms such as
push-pull wires manually or via computer control
[0011] The deployment catheter may also be stabilized relative to
the tissue surface through various methods. For instance,
inflatable stabilizing balloons positioned along a length of the
catheter may be utilized, or tissue engagement anchors may be
passed through or along the deployment catheter for temporary
engagement of the underlying tissue.
[0012] In operation, after the imaging hood has been deployed,
fluid may be pumped at a positive pressure through the fluid
delivery lumen until the fluid fills the open area completely and
displaces any blood from within the open area. The fluid may
comprise any biocompatible fluid, e.g., saline, water, plasma,
Fluorinert.TM., etc., which is sufficiently transparent to allow
for relatively undistorted visualization through the fluid. The
fluid may be pumped continuously or intermittently to allow for
image capture by an optional processor which may be in
communication with the assembly.
[0013] In an exemplary variation for imaging tissue surfaces within
a heart chamber containing blood, the tissue imaging and treatment
system may generally comprise a catheter body having a lumen
defined therethrough, a visualization element disposed adjacent the
catheter body, the visualization element having a field of view, a
transparent fluid source in fluid communication with the lumen, and
a barrier or membrane extendable from the catheter body to
localize, between the visualization element and the field of view,
displacement of blood by transparent fluid that flows from the
lumen, and an instrument translatable through the displaced blood
for performing any number of treatments upon the tissue surface
within the field of view. The imaging hood may be formed into any
number of configurations and the imaging assembly may also be
utilized with any number of therapeutic tools which may be deployed
through the deployment catheter.
[0014] More particularly in certain variations, the tissue
visualization system may comprise components including the imaging
hood, where the hood may further include a membrane having a main
aperture and additional optional openings disposed over the distal
end of the hood. An introducer sheath or the deployment catheter
upon which the imaging hood is disposed may further comprise a
steerable segment made of multiple adjacent links which are
pivotably connected to one another and which may be articulated
within a single plane or multiple planes. The deployment catheter
itself may be comprised of a multiple lumen extrusion, such as a
four-lumen catheter extrusion, which is reinforced with braided
stainless steel fibers to provide structural support. The proximal
end of the catheter may be coupled to a handle for manipulation and
articulation of the system.
[0015] To provide visualization, an imaging element such as a
fiberscope or electronic imager such as a solid state camera, e.g.,
CCD or CMOS, may be mounted, e.g., on a shape memory wire, and
positioned within or along the hood interior. A fluid reservoir
and/or pump (e.g., syringe, pressurized intravenous bag, etc.) may
be fluidly coupled to the proximal end of the catheter to hold the
translucent fluid such as saline or contrast medium as well as for
providing the pressure to inject the fluid into the imaging
hood.
[0016] In clearing the hood of blood and/or other bodily fluids, it
is generally desirable to purge the hood in an efficient manner by
minimizing the amount of clearing fluid, such as saline, introduced
into the hood and thus into the body. As excessive saline delivered
into the blood stream of patients with poor ventricular function
may increase the risk of heart failure and pulmonary edema,
minimizing or controlling the amount of saline discharged during
various therapies, such as atrial fibrillation ablation, atrial
flutter ablation, transseptal puncture, etc. may be generally
desirable.
[0017] In utilizing the devices and systems to access and image
tissue, particular tissue regions within the body to be visualized
and/or treated may undergo occasional or constant movement in vivo.
For instance, organs such as the lungs constantly expand and
contract while the patient undergoes respiration and other organs
such as the heart constantly contract to pump blood through the
body. Because of this tissue movement, acquiring a tissue image
and/or other physiologic data taken at a first instance may present
a condition which is inconsistent with the tissue image and/or
physiologic data taken at a second instance. Accordingly, being
able to acquire images and/or physiologic data of a particular
tissue region at a first point during tissue movement and at
additional points during subsequent tissue movements taken
consistently when the tissue is similarly situated may present a
more accurate representation of the condition for evaluation of the
tissue region being examined and/or treated. To accurately assess
and/or treat a particular tissue region despite this movement of
tissue, e.g., a tissue region located within an atrial chamber
within the beating heart, methods may be utilized to minimize the
effect of this movement on obtained data.
[0018] One method may involve gating the acquisition of the tissue
images and/or corresponding data by utilizing a reference signal
produced by the body for coordinating the corresponding acquisition
of information. For gated acquisition of information, such as the
captured visual images of the tissue and/or corresponding
physiologic parameters, the acquisition of the information may be
triggered by a sensed event, e.g., the QRS complex recorded from a
single heartbeat of the electrocardiogram (ECG) which corresponds
to a depolarization of the right and left ventricles. Once a
triggering event is identified, the system may acquire information
at a specific interval and/or for a specific duration based upon
that predetermined triggering event.
[0019] Although this and other examples describe the gated
acquisition of information based upon the patient's ECG
measurements, other gated acquisition events may also be utilized
herein. For example, gated acquisition may also be utilized for
obtaining images and/or other data based on chest-wall motion for
respiratory-gated acquisition of data.
[0020] Another method for may involve retrospective gating of the
data where information, such as visual images and/or other
physiologic data, may be acquired continuously from the tissue
region. This allows for the capturing of information over several
cycles of the organ or tissue region of interest. By calculating or
determining a timing delay within the captured data, the
information can be reconstructed at one or more specified points
over many heart beats relative to a predetermined reference or
triggering signal. This may allow for a "snapshot" of the heart to
be reconstructed at a specific phase within the cardiac cycle with
the information for this "snapshot" acquired over several beating
cycles which may or may not have occurred at regular intervals.
[0021] Ablation treatment of various tissue regions may also be
optimized by determining the thickness of the tissue region to be
treated and adjusting the ablation parameters accordingly based
upon this thickness. Aside from tissue thickness and ablation
parameters, it may be also useful to monitor the temperature and/or
electrical potential of the tissue surface during the ablative
process.
[0022] Aside from or in addition to the different modalities for
monitoring tissue parameters, visually assessing the tissue region
undergoing ablation may present difficulties in distinguishing
between different regions of the tissue due to limitations in the
imaging sensors or equipment. One method for improving the visual
images of the imaged tissue for assessment by the user may include
adjusting the contrast of the captured images. Contrast allows for
different tissue regions to be distinguished visually from one
another within an image or video. Digital imaging systems such as
CMOS image sensors or CCD camera systems have light sensitivities
which vary with the wavelength of light. Thus, altering the
chromaticity or color of illumination used during imaging could
emphasize or de-emphasize certain colors within the imaged field or
the change in illumination color composition could target the
sensitivity of the image sensor.
[0023] With the detection of multiple lesions along a tissue
region, the unique shape of each lesion may be used to determine
the "address" of that particular lesion. An edge finding, texture
classification, or morphology algorithm may be used to determine
the outline, surface pattern, or shape of the lesion from the
visual information provided by the visualization device. This
information and/or an image depicting the ablation lesion is then
constructed into an array and tagged with the appropriate data such
as the RF power and the length of time ablation took place to
create the particular lesion. Alternatively, lesion identification
may be accomplished via the usage of color comparison algorithms
and/or biological markers on the lesions among other identifiers.
This information may be particularly useful for re-identification,
comparison and mapping of all lesions on the tissue surface.
[0024] When providing real-time visual images for the purposes of
tissue diagnosis or treatment, it may be useful to overlay relevant
information to aid the physician during diagnosis and/or treatment.
Any number of physiologic or treatment parameters may be overlaid
directly upon the monitor for display to the user to facilitate
assessment or treatment, e.g., for estimating the depth of the
lesion formed. In various examples, treatment information (e.g.,
positional information, applied power levels, time of ablation
treatment, etc.) may be superimposed on the image of lesion or any
other additional information (e.g., applied voltage, tissue
thickness, etc.) may also be displayed upon the monitor for display
to the user.
[0025] Yet another example of an informational overlay which may
facilitate tissue treatment assessment may incorporate the distance
of a tissue region to be treated (or undergoing treatment) to a
predetermined anatomical object or location. It is also possible to
overlay information relating to particular metrics on the monitor
during visualization or ablation. Such overlays may be utilized to
determine, e.g., the surface size of the lesion precisely to
facilitate physician assessment of lesion size. It may also be used
to accurately measure anatomical features in the body.
[0026] Aside from measuring anatomical features, another feature
which physicians may utilize with the captured visual images of
tissue may also include the monitoring of changes in color of a
lesion formed over time. Tissue color may be used as a good
indicator of the stage of completion of the lesion forming process
as normal, unablated myocardial tissue is characteristically pink
or red in color. Having these images simultaneously displayed may
provide contextual information to the user in determining whether
sufficient ablation had occurred in the tissue being treated.
[0027] Additionally and/or alternatively, a processor may control
the flow of the purging fluid which may also be used to conduct a
current to the tissue to be treated. It is generally desirable to
deliver the lowest amount of saline to the patient through the hood
as an excessive flow of saline may cause the balance of
electrolytes in the body to fluctuate potentially resulting in
hyponatremia. Yet another parameter utilizing the captured visual
images during tissue ablation may include the detection of bubbles
during ablation. The formation of bubbles may be visible on the
monitor near or at the edges of the visual field and these bubbles
may be generally indicative of high rates of heating,
over-blanching of tissue, or a potential steam popping. The visual
image may be processed by a processor to find locations of any
"hotspots", i.e., areas of high reflection, which may be indicative
of the presence of bubbles.
[0028] In yet another example for processing captured visual images
of tissue regions, the region being visualized may move continually
making it difficult to observe the tissue or to perform any
procedures upon the tissue. Such movement can be monitored visually
by several methods such that the user is able to determine an
appropriate time to begin a procedure. With the distance of hood
movement known, a procedure may be initiated and/or stopped
appropriate each time the hood is expected to move such that
treatment may be synchronized according to hood and tissue
movement.
[0029] In yet another example of utilizing the captured images,
bubbles may be visible in the field of view and thus alert the user
that the hood positioning along the tissue may require
readjustment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1A shows a side view of one variation of a tissue
imaging apparatus during deployment from a sheath or delivery
catheter.
[0031] FIG. 1B shows the deployed tissue imaging apparatus of FIG.
1A having an optionally expandable hood or sheath attached to an
imaging and/or diagnostic catheter.
[0032] FIG. 1C shows an end view of a deployed imaging
apparatus.
[0033] FIGS. 2A and 2B show one example of a deployed tissue imager
positioned against or adjacent to the tissue to be imaged and a
flow of fluid, such as saline, displacing blood from within the
expandable hood.
[0034] FIGS. 3A and 3B show examples of various visualization
imagers which may be utilized within or along the imaging hood.
[0035] FIGS. 4A and 4B show perspective and end views,
respectively, of an imaging hood having at least one layer of a
transparent elastomeric membrane over the distal opening of the
hood.
[0036] FIGS. 5A and 5B show perspective and end views,
respectively, of an imaging hood which includes a membrane with an
aperture defined therethrough and a plurality of additional
openings defined over the membrane surrounding the aperture.
[0037] FIG. 6 shows a perspective assembly view of the steerable
section of a catheter having a distal section with connected links
configured to allow for multi-directional articulation, e.g.,
four-way articulation, and a proximal section with connected links
configured to allow for articulation within a single plane, e.g.,
one-way articulation.
[0038] FIG. 7 illustrates an assembly view of a visualization and
treatment system advanced intravascularly into a patient's heart
for diagnosis and/or treatment.
[0039] FIG. 8A shows a flowchart illustrating one example for
synchronizing visual images of tissue with electrocardiogram data
to capture images of consistent regions of tissue.
[0040] FIG. 8B shows an example of how visual images of tissue may
be captured at coordinated intervals.
[0041] FIGS. 9A and 9B show, respectively, a schematic illustration
and representative graph of a tissue region undergoing ablation and
the temperature differential resulting between the tissue surface
and underlying tissue region.
[0042] FIG. 9C shows a flowchart illustrating one example for
determining suitable ablation parameters for a given thickness of
tissue.
[0043] FIG. 10 shows a flowchart illustrating one method for
monitoring tissue temperature during ablation treatment.
[0044] FIG. 11 shows a flowchart illustrating one method for
improving a contrast level of visualized tissue to improve the
image clarity.
[0045] FIGS. 12A and 12B show an illustrative example of a map of
lesions created over a tissue region and a generated table of the
corresponding parameters for each lesion.
[0046] FIGS. 13A and 13B illustrate an example of a first lesion
created along a tissue region and the corresponding visual image
through the hood and generated map of lesion location.
[0047] FIGS. 14A and 14B illustrate another example of a second
lesion and the corresponding visual image and generated map
indicating relative lesion location.
[0048] FIGS. 15A and 15B illustrate another example of a third
lesion and the corresponding visual image and generated map again
indicating relative lesion location.
[0049] FIG. 16 illustrates a visualized image of tissue with an
example of a generated informational overlay imposed upon or in
proximity to the visualized image indicating certain parameters,
e.g., lesion location, power levels, ablation times, etc.
[0050] FIGS. 17A and 17B illustrate examples of a visualized region
of tissue having its measured electrical potential overlaid upon
the image prior to and during or after ablation.
[0051] FIGS. 18A and 18B illustrate examples of a visualized region
of tissue having its measured temperature overlaid upon the image
prior to and during or after ablation.
[0052] FIG. 19 shows an example of a visualized image of region
with specified informational data, such as distance from a lesion
to a specified anatomical feature, overlaid upon the image.
[0053] FIG. 20 shows an example of a visualized region of tissue
with specified information data, such as lesion length, overlaid
upon the image.
[0054] FIGS. 21A and 21B show examples of a visualized region of
tissue which is treated or has been treated by formation of a
lesion while images the same region is captured during the ablation
process for comparison.
[0055] FIG. 22 shows an example for visually monitoring a degree of
blanching of a tissue region undergoing ablation treatment.
[0056] FIG. 23 shows an example for monitoring and/or controlling a
flow of saline before and/or during ablation treatment.
[0057] FIG. 24 shows an example for visually monitoring bubble
formation on tissue during ablation.
[0058] FIGS. 25A and 25B illustrate an example of inadvertent hood
movement over a tissue region and the resulting change in the
visual field.
[0059] FIGS. 26A and 26B illustrate an example of incomplete hood
apposition against the tissue surface and the resulting formation
of bubbles along one side of the visual field.
DETAILED DESCRIPTION OF THE INVENTION
[0060] Reconfiguring a tissue visualization and treatment device
from a low profile delivery configuration for intravascular
delivery through the vessels of a patient to a deployed and
expanded configuration may subject the distal end effector used for
visualization and/or treatment, such as energy delivery, to
potentially severe mechanical stresses (e.g., torsion, compression,
tension, shearing, etc.). For example, a reconfigurable hood which
undergoes a shape change from its collapsed configuration to an
expanded conical shape may utilize a distensible, collapsible,
and/or reconfigurable substrate which may utilize electrode
placement and electrical connection assemblies which are robust and
able to withstand such stresses. Such electrical connection
assemblies may be shielded or insulated from contacting other
structures so as to present a smooth or unobstructive profile for
reconfiguring with the hood.
[0061] Turning now to the tissue-imaging and manipulation apparatus
upon which one or more electrodes may be positioned and which is
able to provide real-time images in vivo of tissue regions within a
body lumen such as a heart, which is filled with blood flowing
dynamically therethrough and is also able to provide intravascular
tools and instruments for performing various procedures upon the
imaged tissue regions. Such an apparatus may be utilized for many
procedures, e.g., facilitating transseptal access to the left
atrium, cannulating the coronary sinus, diagnosis of valve
regurgitation/stenosis, valvuloplasty, atrial appendage closure,
arrhythmogenic focus ablation, among other procedures.
[0062] One variation of a tissue access and imaging apparatus is
shown in the detail perspective views of FIGS. 1A to 1C. As shown
in FIG. 1A, tissue imaging and manipulation assembly 10 may be
delivered intravascularly through the patient's body in a
low-profile configuration via a delivery catheter or sheath 14. In
the case of treating tissue, it is generally desirable to enter or
access the left atrium while minimizing trauma to the patient. To
non-operatively effect such access, one conventional approach
involves puncturing the intra-atrial septum from the right atrial
chamber to the left atrial chamber in a procedure commonly called a
transseptal procedure or septostomy. For procedures such as
percutaneous valve repair and replacement, transseptal access to
the left atrial chamber of the heart may allow for larger devices
to be introduced into the venous system than can generally be
introduced percutaneously into the arterial system.
[0063] When the imaging and manipulation assembly 10 is ready to be
utilized for imaging tissue, imaging hood 12 may be advanced
relative to catheter 14 and deployed from a distal opening of
catheter 14, as shown by the arrow. Upon deployment, imaging hood
12 may be unconstrained to expand or open into a deployed imaging
configuration, as shown in FIG. 1B. Imaging hood 12 may be
fabricated from a variety of pliable or conformable biocompatible
material including but not limited to, e.g., polymeric, plastic, or
woven materials. One example of a woven material is Kevlar.RTM. (E.
I. du Pont de Nemours, Wilmington, Del.), which is an aramid and
which can be made into thin, e.g., less than 0.001 in., materials
which maintain enough integrity for such applications described
herein. Moreover, the imaging hood 12 may be fabricated from a
translucent or opaque material and in a variety of different colors
to optimize or attenuate any reflected lighting from surrounding
fluids or structures, i.e., anatomical or mechanical structures or
instruments. In either case, imaging hood 12 may be fabricated into
a uniform structure or a scaffold-supported structure, in which
case a scaffold made of a shape memory alloy, such as Nitinol, or a
spring steel, or plastic, etc., may be fabricated and covered with
the polymeric, plastic, or woven material. Hence, imaging hood 12
may comprise any of a wide variety of barriers or membrane
structures, as may generally be used to localize displacement of
blood or the like from a selected volume of a body lumen or heart
chamber. In exemplary embodiments, a volume within an inner surface
13 of imaging hood 12 will be significantly less than a volume of
the hood 12 between inner surface 13 and outer surface 11.
[0064] Imaging hood 12 may be attached at interface 24 to a
deployment catheter 16 which may be translated independently of
deployment catheter or sheath 14. Attachment of interface 24 may be
accomplished through any number of conventional methods. Deployment
catheter 16 may define a fluid delivery lumen 18 as well as an
imaging lumen 20 within which an optical imaging fiber or assembly
may be disposed for imaging tissue. When deployed, imaging hood 12
may expand into any number of shapes, e.g., cylindrical, conical as
shown, semi-spherical, etc., provided that an open area or field 26
is defined by imaging hood 12. The open area 26 is the area within
which the tissue region of interest may be imaged. Imaging hood 12
may also define an atraumatic contact lip or edge 22 for placement
or abutment against the tissue region of interest. Moreover, the
diameter of imaging hood 12 at its maximum fully deployed diameter,
e.g., at contact lip or edge 22, is typically greater relative to a
diameter of the deployment catheter 16 (although a diameter of
contact lip or edge 22 may be made to have a smaller or equal
diameter of deployment catheter 16). For instance, the contact edge
diameter may range anywhere from 1 to 5 times (or even greater, as
practicable) a diameter of deployment catheter 16. FIG. 1C shows an
end view of the imaging hood 12 in its deployed configuration. Also
shown are the contact lip or edge 22 and fluid delivery lumen 18
and imaging lumen 20.
[0065] As seen in the example of FIGS. 2A and 2B, deployment
catheter 16 may be manipulated to position deployed imaging hood 12
against or near the underlying tissue region of interest to be
imaged, in this example a portion of annulus A of mitral valve MV
within the left atrial chamber. As the surrounding blood 30 flows
around imaging hood 12 and within open area 26 defined within
imaging hood 12, as seen in FIG. 2A, the underlying annulus A is
obstructed by the opaque blood 30 and is difficult to view through
the imaging lumen 20. The translucent fluid 28, such as saline, may
then be pumped through fluid delivery lumen 18, intermittently or
continuously, until the blood 30 is at least partially, and
preferably completely, displaced from within open area 26 by fluid
28, as shown in FIG. 2B.
[0066] Although contact edge 22 need not directly contact the
underlying tissue, it is at least preferably brought into close
proximity to the tissue such that the flow of clear fluid 28 from
open area 26 may be maintained to inhibit significant backflow of
blood 30 back into open area 26. Contact edge 22 may also be made
of a soft elastomeric material such as certain soft grades of
silicone or polyurethane, as typically known, to help contact edge
22 conform to an uneven or rough underlying anatomical tissue
surface. Once the blood 30 has been displaced from imaging hood 12,
an image may then be viewed of the underlying tissue through the
clear fluid 30. This image may then be recorded or available for
real-time viewing for performing a therapeutic procedure. The
positive flow of fluid 28 may be maintained continuously to provide
for clear viewing of the underlying tissue. Alternatively, the
fluid 28 may be pumped temporarily or sporadically only until a
clear view of the tissue is available to be imaged and recorded, at
which point the fluid flow 28 may cease and blood 30 may be allowed
to seep or flow back into imaging hood 12. This process may be
repeated a number of times at the same tissue region or at multiple
tissue regions.
[0067] FIG. 3A shows a partial cross-sectional view of an example
where one or more optical fiber bundles 32 may be positioned within
the catheter and within imaging hood 12 to provide direct in-line
imaging of the open area within hood 12. FIG. 3B shows another
example where an imaging element 34 (e.g., CCD or CMOS electronic
imager) may be placed along an interior surface of imaging hood 12
to provide imaging of the open area such that the imaging element
34 is off-axis relative to a longitudinal axis of the hood 12, as
described in further detail below. The off-axis position of element
34 may provide for direct visualization and uninhibited access by
instruments from the catheter to the underlying tissue during
treatment.
[0068] In utilizing the imaging hood 12 in any one of the
procedures described herein, the hood 12 may have an open field
which is uncovered and clear to provide direct tissue contact
between the hood interior and the underlying tissue to effect any
number of treatments upon the tissue, as described above. Yet in
additional variations, imaging hood 12 may utilize other
configurations. An additional variation of the imaging hood 12 is
shown in the perspective and end views, respectively, of FIGS. 4A
and 4B, where imaging hood 12 includes at least one layer of a
transparent elastomeric membrane 40 over the distal opening of hood
12. An aperture 42 having a diameter which is less than a diameter
of the outer lip of imaging hood 12 may be defined over the center
of membrane 40 where a longitudinal axis of the hood intersects the
membrane such that the interior of hood 12 remains open and in
fluid communication with the environment external to hood 12.
Furthermore, aperture 42 may be sized, e.g., between 1 to 2 mm or
more in diameter and membrane 40 can be made from any number of
transparent elastomers such as silicone, polyurethane, latex, etc.
such that contacted tissue may also be visualized through membrane
40 as well as through aperture 42.
[0069] Aperture 42 may function generally as a restricting
passageway to reduce the rate of fluid out-flow from the hood 12
when the interior of the hood 12 is infused with the clear fluid
through which underlying tissue regions may be visualized. Aside
from restricting out-flow of clear fluid from within hood 12,
aperture 42 may also restrict external surrounding fluids from
entering hood 12 too rapidly. The reduction in the rate of fluid
out-flow from the hood and blood in-flow into the hood may improve
visualization conditions as hood 12 may be more readily filled with
transparent fluid rather than being filled by opaque blood which
may obstruct direct visualization by the visualization
instruments.
[0070] Moreover, aperture 42 may be aligned with catheter 16 such
that any instruments (e.g., piercing instruments, guidewires,
tissue engagers, etc.) that are advanced into the hood interior may
directly access the underlying tissue uninhibited or unrestricted
for treatment through aperture 42. In other variations wherein
aperture 42 may not be aligned with catheter 16, instruments passed
through catheter 16 may still access the underlying tissue by
simply piercing through membrane 40.
[0071] In an additional variation, FIGS. 5A and 5B show perspective
and end views, respectively, of imaging hood 12 which includes
membrane 40 with aperture 42 defined therethrough, as described
above. This variation includes a plurality of additional openings
44 defined over membrane 40 surrounding aperture 42. Additional
openings 44 may be uniformly sized, e.g., each less than 1 mm in
diameter, to allow for the out-flow of the translucent fluid
therethrough when in contact against the tissue surface. Moreover,
although openings 44 are illustrated as uniform in size, the
openings may be varied in size and their placement may also be
non-uniform or random over membrane 40 rather than uniformly
positioned about aperture 42 in FIG. 5B. Furthermore, there are
eight openings 44 shown in the figures although fewer than eight or
more than eight openings 44 may also be utilized over membrane
40.
[0072] Additional details of tissue imaging and manipulation
systems and methods which may be utilized with apparatus and
methods described herein are further described, for example, in
U.S. patent application Ser. No. 11/259,498 filed Oct. 25, 2005
(U.S. Pat. Pub. 2006/0184048 A1), which is incorporated herein by
reference in its entirety.
[0073] In utilizing the devices and methods above, various
procedures may be accomplished. One example of such a procedure is
crossing a tissue region such as in a transseptal procedure where a
septal wall is pierced and traversed, e.g., crossing from a right
atrial chamber to a left atrial chamber in a heart of a subject.
Generally, in piercing and traversing a septal wall, the
visualization and treatment devices described herein may be
utilized for visualizing the tissue region to be pierced as well as
monitoring the piercing and access through the tissue. Details of
transseptal visualization catheters and methods for transseptal
access which may be utilized with the apparatus and methods
described herein are described in U.S. patent application Ser. No.
11/763,399 filed Jun. 14, 2007 (U.S. Pat. Pub. 2007/0293724 A1),
which is incorporated herein by reference in its entirety.
Additionally, details of tissue visualization and manipulation
catheter which may be utilized with apparatus and methods described
herein are described in U.S. patent application Ser. No. 11/259,498
filed Oct. 25, 2005 (U.S. Pat. Pub. 2006/0184048 A1), which is
incorporated herein by reference in its entirety.
[0074] In clearing the hood of blood and/or other bodily fluids, it
is generally desirable to purge the hood in an efficient manner by
minimizing the amount of clearing fluid, such as saline, introduced
into the hood and thus into the body. As excessive saline delivered
into the blood stream of patients with poor ventricular function
may increase the risk of heart failure and pulmonary edema,
minimizing or controlling the amount of saline discharged during
various therapies, such as atrial fibrillation ablation, atrial
flutter ablation, transseptal puncture, etc. may be generally
desirable.
[0075] Turning now to the electrode assemblies and connection
systems utilized with the collapsible hood, various examples are
described herein which illustrate variations for electrode
positioning along the hood which may minimize or reduce the degree
of stress imparted to the electrode assemblies. These electrodes
(e.g., electrode pairs) may be used to deliver electrical energy
such as radio-frequency energy to tissue in direct contact with or
in proximity to the electrodes to form lesions upon the tissue
surface as well as underlying tissue regions. Additionally, the
electrodes or electrode pairs may be positioned about the hood in a
uniform or non-uniform manner depending upon the desired
configuration. Moreover, these electrodes may also be used to
deliver energy into and/or through the purging fluid which may
contact the electrodes for conducting the energy through the fluid
and into the underlying tissue region being treated. Alternatively,
one or more of these electrodes may also be used to detect and/or
measure any electrophysiological activity of the contacted tissue
prior to, during, or after tissue treatment.
[0076] While specific examples of the visualization and treatment
hood are shown herein, other variations and examples of hoods and
tissue treatment systems may be utilized with the devices and
methods described herein. For example, the hoods, systems, and
other features as described in Ser. No. 11/259,498 filed Oct. 25,
2005 (U.S. Pat. Pub. 2006/0184048 A1); Ser. No. 11/775,837 filed
Jul. 10, 2007 (U.S. Pat. Pub. 2008/0009747 A1); Ser. No. 11/828,267
filed Jul. 25, 2007 (U.S. Pat. Pub. No. 2008/0033290 A1); Ser. No.
12/118,439 filed May 9, 2008 (U.S. Pat. Pub. 2009/0030412 A1); Ser.
No. 12/201,811 filed Aug. 29, 2008 (U.S. Pat. Pub. 2009/0062790
A1); and Ser. No. 12/209,057 filed Sep. 11, 2008 (U.S. Pat. Pub.
20090076498 A1), may be utilized herewith. Each of these
applications is incorporated herein by reference in its
entirety.
[0077] In particular, such assemblies, apparatus, and methods may
be utilized for treatment of various conditions, e.g., arrhythmias,
through ablation under direct visualization. Details of examples
for the treatment of arrhythmias under direct visualization which
may be utilized with apparatus and methods described herein are
described, for example, in U.S. patent application Ser. No.
11/775,819 filed Jul. 10, 2007 (U.S. Pat. Pub. No. 2008/0015569
A1), which is incorporated herein by reference in its entirety.
Variations of the tissue imaging and manipulation apparatus may be
configured to facilitate the application of bipolar energy
delivery, such as radio-frequency (RF) ablation, to an underlying
target tissue for treatment in a controlled manner while directly
visualizing the tissue during the bipolar ablation process as well
as confirming (visually and otherwise) appropriate treatment
thereafter.
[0078] Turning now to the perspective assembly view of FIG. 6, one
variation of an articulatable deployment catheter 50 is shown which
comprises a distal steerable section 52 and a proximal steerable
section 54 located proximally of the distal steerable section 52.
Further details of the deployment catheter 50 which may be used
herein may be seen in further detail in U.S. patent application
Ser. No. 12/108,812 filed Apr. 24, 2008 (U.S. Pat. Pub. No.
2008/0275300 A1), which is incorporated herein by reference in its
entirety. An intervening link 56 may couple the sections 52, 54 to
one another and provide a terminal link to which one or more pull
wires may be attached in controlling one or both sections. The
distal steerable section 52 may utilize individual links 66 which
allow for the section 52 to be articulated in a variety of
different directions and angles, e.g., four-way steering, to enable
omni-direction articulation. The individual links 66 may
accordingly utilize a body member 68 having a pair of yoke members
70 positioned opposite to one another and extending distally from
the body member 68 and each defining an opening. A pair of pins 72
may each extend radially in opposing directions from body member 68
and in a perpendicular plane relative to a plane defined by the
yoke members 70. The pins 72 of each link 66 may be pivotably
received by the yoke members 70 of an adjacent link 66 such that
the pins 72 and yoke members 70 are joined in an alternating
manner. This alternating connection allows for the serially aligned
links 66 to be articulated omni-directionally.
[0079] The links 58 of the proximal steering section 54 may also
comprise a pair of yoke members 62 positioned opposite to one
another and extending distally from body member 60. However, the
pins 64 may extend radially in opposing directions while remaining
in the same plane as that defined by yoke members 62. When joined
together in series, each pin 64 of each link 58 may be pivotably
received by the yoke members 62 of an adjacent link 58. Yet when
joined, the composite proximal steering section 54 may be
constrained to bend planarly within a single plane relative to the
rest of the deployment catheter.
[0080] The combined distal steerable section 52 and a proximal
steerable section 54 results in a proximal steering section which
can be articulated in a single plane to retroflex the entire distal
assembly and a distal steering section which can then be
articulated any number of directions, e.g., four-way steering, to
access anatomical structures within the heart or any other lumen.
The assembly may thus be used, e.g., to create circumferential
lesions around the ostia of the pulmonary veins in the left atrium
while the underlying tissue remains under direct visualization
through the hood.
[0081] In utilizing the catheter 50 or other suitable catheter
system, FIG. 7 shows an illustrative assembly of how a
visualization catheter system may be configured and advanced
intravascularly within a patient. Further details of the system
which may be used herein may be seen in further detail in U.S.
patent application Ser. No. 12/323,281 filed Nov. 25, 2008 (U.S.
Pat. Pub. No. 2009/0143640 A1), which is incorporated herein by
reference in its entirety.
[0082] FIG. 7 illustrates a perspective assembly view of an
endoscope 108 introduced within seal 94 and deployment catheter 88.
Hood 12 can be first collapsed by hood retraction control 98 while
saline is purged through hood 12 to ensure no bubbles are trapped
inside hood 12. Catheter 88 may be advanced within introducer
sheath 106 for deployment within the patient body. Additionally,
introducer sheath 106 may further include a fluid irrigation port
104 extending from sheath 106 for coupling to a fluid reservoir or
for providing access to other instruments into the patient body.
The variation shown also illustrates an example where an additional
endoscope handle interface may be attached to hub 100 for
facilitating coupling and de-coupling to endoscope handle 102.
[0083] Hood 12 and deployment catheter 88 may be advanced through
introducer sheath 106 into the patient's vasculature, e.g., through
the inferior vena cava IVC and transseptally into the left atrium
LA of the patient's heart H, where tissue regions may be treated,
such as lesion creation around the ostia of the pulmonary veins for
treatment of atrial fibrillation. Once hood 12 has been advanced
into the left atrium LA, hood 12 may be deployed to expand for
visualization and tissue treatment. Hood 12 may be purged via
saline fluid from reservoir 82 introduced through port 96 while an
electrode assembly along hood 12 may be utilized to detect, e.g.,
ECG signals 90, or to ablate tissue via generator 80. These
electrical signals may be detected and/or delivered via the
electrode assembly which may be electrically coupled through
catheter 88 to a processor and/or video display, e.g.,
electrocardiogram (ECG) display, via junction 92, which may also be
electrically coupled to generator 80 for providing power, e.g., RF
energy, to the electrode assembly. The underlying tissue may be
visualized via the endoscope imaging assembly which may in turn be
coupled to video processor assembly 84 which may capture and
process the detected images within hood 12 for display upon monitor
86. Alternatively, hood 12 may be purged via fluid introduced
through a fluid lumen defined through the endoscope itself.
[0084] The working channel of the endoscope and/or irrigation port
can also be used to introduce guidewires, needles (such as
transseptal or biologics delivery needles), dilators, ablation
catheters (such as RF, cryo, ultrasound, laser and microwave),
temperature monitoring probes, PFO closure devices, LAA closure
implants, coronary artery stents, or other implantable devices or
tools for performing diagnosis and/or treatment of the imaged
target tissue. These lumens can also be used for the suction and/or
evacuation of blood clots and/or any tissue debris as well as for
the injection of contrast media for fluoroscopic imaging.
[0085] In utilizing the devices and systems to access and image
tissue, particular tissue regions within the body to be visualized
and/or treated may undergo occasional or constant movement in vivo.
For instance, organs such as the lungs constantly expand and
contract while the patient undergoes respiration and other organs
such as the heart constantly contract to pump blood through the
body. Because of this tissue movement, acquiring a tissue image
and/or other physiologic data taken at a first instance may present
a condition which is inconsistent with the tissue image and/or
physiologic data taken at a second instance. Accordingly, being
able to acquire images and/or physiologic data of a particular
tissue region at a first point during tissue movement and at
additional points during subsequent tissue movements taken
consistently when the tissue is similarly situated may present a
more accurate representation of the condition for evaluation of the
tissue region being examined and/or treated. To accurately assess
and/or treat a particular tissue region despite this movement of
tissue, e.g., a tissue region located within an atrial chamber
within the beating heart, methods may be utilized to minimize the
effect of this movement on obtained data.
[0086] One method may involve gating the acquisition of the tissue
images and/or corresponding data by utilizing a reference signal
produced by the body for coordinating the corresponding acquisition
of information. For gated acquisition of information, such as the
captured visual images of the tissue and/or corresponding
physiologic parameters, the acquisition of the information may be
triggered by a sensed event, e.g., the QRS complex recorded from a
single heartbeat of the electrocardiogram (ECG) which corresponds
to a depolarization of the right and left ventricles. Once a
triggering event is identified, the system may acquire information
at a specific interval and/or for a specific duration based upon
that predetermined triggering event.
[0087] Although this and other examples describe the gated
acquisition of information based upon the patient's ECG
measurements, other gated acquisition events may also be utilized
herein. For example, gated acquisition may also be utilized for
obtaining images and/or other data based on chest-wall motion for
respiratory-gated acquisition of data.
[0088] Another method for may involve retrospective gating of the
data where information, such as visual images and/or other
physiologic data, may be acquired continuously from the tissue
region. This allows for the capturing of information over several
cycles of the organ or tissue region of interest. By calculating or
determining a timing delay within the captured data, the
information can be reconstructed at one or more specified points
over many heart beats relative to a predetermined reference or
triggering signal. This may allow for a "snapshot" of the heart to
be reconstructed at a specific phase within the cardiac cycle with
the information for this "snapshot" acquired over several beating
cycles which may or may not have occurred at regular intervals.
[0089] Generally, when two-dimensional images of a moving organ,
such as the heart, are captured the images are built up over time
in synchronization with respect to the movement of the organ. For
example, CT images of the heart may be captured in synchronization
with a sensed ECG signal such that all the CT image slices are
generated at the same point during the heart cycle. In the absence
of such synchronization, the three-dimensional images may be
blurred rendering them unsuitable for analysis. Additionally and/or
alternatively, images of the organs may also be synchronized with
the respiratory cycle, as previously mentioned.
[0090] When anatomical features, electro-anatomical maps, or any
other real-time data is to be registered against real-time visual
images of the heart or any other moving organ, a determination of
which cycle the image was acquired may be used to achieve proper
registration between the data and the corresponding image.
Generally, one or more visual images may be collected
simultaneously with the sensed ECG data. An example for
synchronizing data, in this case ECG data, with real-time visual
images is illustrated in the flowchart 110, as shown in FIG. 8A.
The hood 12 may be advanced intravascularly, e.g., into a heart
chamber such as the left atrial chamber, where it may be presented
against a tissue region of interest moving as the heart continues
to beat. The hood 12 may be cleared, as previously described, and
one or more images of the underlying tissue may be acquired 112.
These one or more images may be buffered 114 and multiple images
may be acquired 116 until sufficient images are captured.
[0091] While the visual images are captured, one or more sensors
located along the hood 12 or separately upon the patient may be
used to simultaneously detect and record ECG data 118. In the event
that a sufficient number of images have been captured, a gating
point may be selected 120 such as during an R wave of the QRS
Complex, although any number of other physiologic triggering points
may be utilized. With the gating point determined, a controller or
processor may select the appropriate visual image 122 which was
captured correspondingly and transmit the visual image data 124 for
comparison. The controller or processor may then adjust the gating
point 126, if necessary, in which case the gating point may be
appropriately adjusted 134 by selecting another appropriate image.
Should the gating point be adjusted to a different gating point, a
new set of corresponding visual images may be displayed. Such
synchronization may allow for visual analysis of the tissue that is
imaged as the impact on the image quality due to the movement of
the tissue may be greatly reduced (for example, due to the
expansion and contraction of the heart). While the visual images
are selected and transmitted, the recorded ECG data may be
extracted 128 and the data may be registered with the corresponding
visual image 130. The final extracted image with the corresponding
ECG data may then be displayed as a composite image 132 to the
user.
[0092] As illustrated in the example of FIG. 8B, a detected and
recorded ECG measurement 140 of a patient is shown and displayed
over several cycles of the heart beating. While the ECG measurement
140 was recorded, the visual images of the tissue region of
interest were simultaneously captured as well. In utilizing the R
wave of the QRS Complex, in this example, as the triggering or
gating point, the visual images of the tissue region captured at
those corresponding times may be extracted and registered
corresponding to each gating point. The image at each gating point
may then be displayed to the user as a composite image, as shown.
Thus, the first gating point 142 shown on the ECG measurement 140
may have a first corresponding image 150 displayed accordingly and
the second gating point 144 may have a second corresponding image
152 displayed accordingly as well. Likewise, third gating point 146
may have third corresponding image 154 displayed while fourth
gating point 148 may have fourth corresponding image 156 displayed,
and so on. In this manner, the visualized tissue region may be
compared between captured images to provide a more accurate
representation of the tissue in any particular state.
[0093] Moreover, cardiac-gating of information allows for
piece-wise data acquisition over multiple heart beats to create a
global view of the heart at a single phase within the cardiac
cycle. For example, within the left ventricle, the end-systolic
phase of the cardiac cycle represents the maximum contraction of
the ventricle. Therefore, the ventricular cavity defines its
relative smallest volume at this phase of the cardiac cycle.
Likewise, the end-diastolic phase of the cardiac cycle represents
the end of the filling period of the left ventricle with blood. The
ventricle is at its maximum or near-maximum volume at this
phase.
[0094] Throughout each cardiac cycle, a point on the endocardial
surface may be displaced in three-dimensional space between these
two phases of the cardiac cycle. To create a three-dimensional map
of the endocardial surface during end-diastole, individual mapping
points may include the relative position (e.g., X, Y, Z
coordinates) to be consistently captured at the point during the
cardiac cycle relative to the reference or gating signal, such as
the ECG signal. These methods could also be applied to the captured
visualization information. In order to capture an image at the same
point in the cardiac cycle, a global reference such as the ECG
signal may be used. Based on timing data relative to a specific
event such as the QRS Complex on the ECG recording, the image could
be correspondingly registered by calculating the timing delays
within the system for data acquisition and processing. These delays
could shift the two data streams relative to one another.
[0095] In treating a tissue region, e.g., via application of energy
such as RF energy to create lesions, one physiologic characteristic
which is usually not readily available to physicians is the
thickness of the tissue at a desired lesion location. It may be
generally useful to know the thickness of the tissue in
facilitating lesion formation by applying an appropriate level of
energy to prevent excessive lesion formation (e.g., lesions which
are larger and/or deeper than desired) in order to prevent damage
to surrounding tissue or anatomy. Information on the tissue
thickness may also be useful to the physician so that the optimal
parameters for ablation may be determined with respect to the speed
of the ablation formation to safely reduce procedural time.
[0096] One of the difficulties in determining appropriate ablation
treatment parameters through the hood 12 may be due to the
temperature gradient formed through the tissue thickness during
ablation treatment. For example, FIG. 9A illustrates an example of
hood 12 placed against a tissue region T to be ablated. As energy
is conducted through hood 12 and into the underlying tissue, a
temperature differential is formed between the tissue surface
T.sub.1 and a region of underlying tissue T.sub.2. As heat is
conducted from the tissue surface T.sub.1 down through the tissue
region T, tissue surface T.sub.1 may undergo ablation first as its
temperature rises quickly during ablation treatment, as indicated
by curve 162, relative to the temperature of the underlying tissue
T.sub.2 which rises slowly over time, as indicated by curve 164,
shown in the ablation time versus temperature graph 160 of FIG.
9B.
[0097] One example for determining the thickness of a tissue region
to be treated and for selecting ablation parameters based on this
thickness is illustrated in the flowchart 170 of FIG. 9C. With the
tissue region to be treated identified visually (or through other
modalities) 172, the tissue thickness may be detected 174
utilizing, e.g., hood 12 having one or more ultrasonic transducers
positioned upon hood 12 or its distal membrane in contact with the
underlying tissue. For example, prior to the initiation of tissue
ablation, the one or more transducers may be placed against the
tissue surface to be treated and ultrasonic signals may be emitted
into the tissue. The emitted signals may be reflected by any
underlying obstructions or tissue interfaces such that the return
signals received by the transducer or receiver may be automatically
processed by a processor to analyze the return signals for peaks of
the ultrasonic waves received and the time intervals between them
to determine a thickness of the underlying tissue. Examples of
ultrasound use with hood 12 are shown and described in greater
detail in U.S. patent application Ser. No. 12/118,439 filed May 9,
2008 (U.S. Pat. Pub. 2009/0030412 A1), which is incorporated herein
by reference in its entirety. Alternatively, tissue thickness may
also be determined by, e.g., sensor triangulation techniques,
trans-esophageal echocardiography or any other methods.
[0098] A nominal tissue thickness may be programmed into a
processor by the user to set a threshold tissue thickness for
safely performing tissue ablation. The detected tissue thickness
may then be compared against this nominal thickness threshold 176.
In the event that the detected thickness exceeds this threshold
tissue thickness, the controller may automatically determine the
appropriate ablation parameters suitable for this detected
thickness 178 such as, power levels (e.g., Watts), flow rate of the
purging/conductive fluid through the hood (e.g., cc/min), ablation
treatment times (e.g., sec), etc. (which may be available on a
table of tissue depth versus power, flow rate, ablation duration,
etc.). This determination may be performed automatically by the
system or by the user and ablation may be started 180 either
automatically or initiated by the user. In the event that the
detected tissue thickness fails to meet the threshold tissue
thickness, the system may alert the user 182 who may then
re-measure the tissue thickness 184. If the re-measured tissue
thickness exceeds the nominal tissue thickness, ablation may
proceed, as previously described, or the operator may determine the
ablation parameters manually 186 and then initiate ablation
180.
[0099] Additional examples of devices and methods which may be
utilized with the systems described herein are further shown in
U.S. Pat. Pub. 2007/0106146 A1, which is incorporated herein by
reference in its entirety.
[0100] Aside from tissue thickness and ablation parameters, it may
be also useful to monitor the temperature of the tissue surface
during the ablative process. Ablation of tissue is typically
performed such that it causes irreversible tissue damage to
selected regions of tissue. The temperature at which irreversible
tissue damage typically occurs is around 53.degree. C. depending on
the tissue thickness. Excessively high temperatures may give rise
to the possibility of bubble formation on the tissue (which may pop
as steam) or tissue charring. Steam pops, which may burst with an
audible popping sound, may disrupt the myocardium and cause
perforations on the tissue surface potentially leading to
complications, such as cardiac tamponade, which may cause the heart
to pump decreasing amount of blood. Charring of tissue may also
allow thrombus formation which may embolize and potentially lead to
stroke, ischemia, and/or myocardial infarction among other
things.
[0101] One example for monitoring tissue temperatures prior to
and/or during tissue ablation is illustrated in the flowchart 190
of FIG. 10. Once the targeted tissue region is identified 192
utilizing the devices and methods described above, the tissue
temperature (surface and/or subsurface tissue temperatures) may be
initially measured 194 utilizing any number of temperature
measurement devices. For example, temperature sensors may be
positioned along the hood 12 and/or distal membrane of the hood in
contact against the tissue surface. Other sensors may include,
e.g., thermocouples, thermistors, fluoro-optic temperature sensors,
thermochromic markers under direct visualization through the hood
12, etc. Thermochromic markers may be embedded within the distal
membrane which may be pressed against the tissue region. Changes in
the marker colors which are indicative of the tissue temperature
changes may be monitored through hood 12 via the imager or via an
automated vision sensing system. Further examples of tissue
temperature sensors and methods of their use are described in
further detail in U.S. patent application Ser. No. 12/118,439,
which is incorporated herein by reference above.
[0102] Additionally, needle probes or similar devices may be
inserted into the tissue region to be treated to provide a
measurement of the sub-surface tissue temperature. Further examples
of sub-surface measurement systems and methods of their use which
may be utilized with the devices and methods described herein are
shown in further detail in U.S. patent application Ser. No.
11/775,837 filed Jul. 10, 2007 (U.S. Pat. Pub. 2008/0009747 A1),
which is incorporated herein by reference in its entirety.
[0103] With the tissue surface and/or sub-surface temperatures
measured, upper T.sub.High and/or lower T.sub.Low limits for the
allowed temperature range are set 196 to ensure adequate power
delivery for therapy yet prevent unwanted complications due to
excessive (or inadequate) energy delivery. The tissue may then be
ablated 198 while the tissue temperature (surface and/or
sub-surface) is monitored. So long as the monitored tissue
temperature remains above the preset lower T.sub.Low temperature
limit 200, ablation may continue 202 unabated. In the event that
the tissue temperature falls below the lower T.sub.Low temperature
limit, an audible or visible indicator may notify the user and/or a
controller may pause the ablation 208. Attention by the user may
allow for adjustment of the ablation treatment and/or preset
temperature limits.
[0104] During ablation treatment, so long as the upper T.sub.High
temperature limit is not exceeded 204, ablation may continue until
the procedure is completed 210 and ablation treatment may be
stopped 212. However, in the event that the monitored tissue
temperature exceeds the upper T.sub.High temperature limit 204, an
audible or visible indicator may notify the user and/or a
controller may pause the ablation 206. Attention by the user may
allow for adjustment of the ablation treatment and/or preset
temperature limits 210 so either allow for continued ablation
treatment 202 or cessation of ablation 212.
[0105] Aside from or in addition to the different modalities for
monitoring tissue parameters, visually assessing the tissue region
undergoing ablation may present difficulties in distinguishing
between different regions of the tissue due to limitations in the
imaging sensors or equipment. One method for improving the visual
images of the imaged tissue for assessment by the user may include
adjusting the contrast of the captured images. Contrast allows for
different tissue regions to be distinguished visually from one
another within an image or video. Digital imaging systems such as
CMOS image sensors or CCD camera systems have light sensitivities
which vary with the wavelength of light. Thus, altering the
chromaticity or color of illumination used during imaging could
emphasize or de-emphasize certain colors within the imaged field or
the change in illumination color composition could target the
sensitivity of the image sensor.
[0106] FIG. 11 shows an example for improving image contrast prior
to and/or during tissue ablation in flowchart 220. Such a method
may be utilized while visually observing tissue ablation through
hood 12 via the imager to improve contrast and differentiation
between regions of, e.g., normal myocardial tissue and regions
where ablation lesions have been created for the treatment of
cardiac arrhythmias such as atrial fibrillation. Generally, images
acquired from the field of view through hood 12 may have their
contrast levels and other relevant characteristics determined and
then compared to previously stored data. If additional contrast is
needed or desired, a processor may be used to increment various
illumination color channels (such as the brightness of different
color LED light sources which combine to provide the illumination).
Following each incremental adjustment, the processor may
re-evaluate the contrast levels and continue to adjust the color
balance of the illumination source. If additional changes in
contrast are determined to be unnecessary or differences in
contrast are nominal or eliminated between comparisons, the
processor may evaluate the output image with respect to the range
limits of this system.
[0107] As shown in flowchart 220, as the images of the tissue
region of interest are captured, this may be done while the system
begins in a default mode 222. During this image acquisition of the
underlying tissue region defined within the field of view of the
hood, the RGB (red, green, blue) values of the images may be
acquired 224 and determined by a processor and then optionally
converted to an HSV (hue, saturation, value) color model (or other
color space) 226 to more accurately describe the perceptual color
relationships. The newly obtained images with their RGB or HSV
values may then be compared and contrasted to a previously obtained
frame or stored frame 228 via the processor. In the event that the
contrast levels are increased 230 in view of the comparison, the
RGB values in the light source illuminating the tissue region may
be increased incrementally and sequentially 232 by the processor
and the entire process repeated until the contrast levels are
equivalent between previously obtained images and newly obtained
images 230. Once the contrast levels have been equalized, the RGB
or HSV values may be compared against predetermined range limits
234 by the processor.
[0108] A comparison of the images against the range limits may
yield RGB values which exceed these limits 236, in which case the
images and/or range limits may be reset and the processor may
perform a diagnostic test on the system 238 and an indication or
warning may alert 240 the user. Otherwise, if the images against
the range limits yield RGB values which are within the limits, then
the contrast levels and light settings may be recorded 242 and the
RGB light source may be set to these values 244 and the
visualization assessment or procedure may proceed 246.
[0109] With the imaging contrast levels appropriately adjusted for
visualizing the tissue region, visualization and/or treatment of
one or more tissue regions may be performed. In the event that
multiple lesions are to be formed over a tissue region, each of
these lesions may necessitate ablation parameters which vary from
one another to optimally treat the tissue region 250 which can vary
physiologically depending upon which region is treated.
Accordingly, the user may automatically track the parameters and
locations which may be unique for each of the lesions formed over
tissue region 250, as shown in FIG. 12A. The table in FIG. 12B
shows an example of how a processor in communication with the
visualization and/or treatment device may catalogue and identify
each formed lesion utilizing visual information captured from the
field of view through the hood 12.
[0110] In one variation, the unique shape of each lesion may be
used to determine the "address" of that particular lesion. An edge
finding, texture classification, or morphology algorithm may be
used to determine the outline, surface pattern, or shape of the
lesion from the visual information provided by the visualization
device. This information and/or an image depicting the ablation
lesion is then constructed into an array and tagged with the
appropriate data such as the RF power and the length of time
ablation took place to create the particular lesion. Accordingly,
first lesion 252 may be identified by its unique shape and/or
relative location and its corresponding power level and ablation
time may be identified on the array. Likewise, each subsequent
lesion, e.g., second lesion 254, third lesion 256, fourth lesion
258, fifth lesion 260, etc. may have its own power level and
ablation time associated accordingly.
[0111] Alternatively, lesion identification may be accomplished via
the usage of color comparison algorithms and/or biological markers
on the lesions among other identifiers. This information may be
particularly useful for re-identification, comparison and mapping
of all lesions on the tissue surface 250. If catheter position
information is available, this information may be combined with the
data of the array of FIG. 12B to automatically map out the ablation
lesions relative to their position within the heart.
[0112] Additional control and navigation systems which may be
utilized herein are shown and described in further detail in U.S.
patent application Ser. No. 11/848,429 filed Aug. 31, 2007 (U.S.
Pat. Pub. 2008/0097476 A1) and in Ser. No. 11/848,532 also filed
Aug. 31, 2007 (U.S. Pat. Pub. 2009/0054803 A1), each of which is
incorporated herein by reference in its entirety.
[0113] When multiple areas along the tissue region 270 have lesions
formed on them, a navigational mini-map may be utilized which
allows the physician to view, track and/or map the multiple lesions
that are formed on the tissue surface during the ablative
treatment. In using the lesion address array previously described,
lesions may be detected and/or their relative location to one
another may be determined by various methods, such as measuring
optical flow as the hood of the catheter moves from one site to
another. This information may be then displayed on a map on the
monitor 278. For example, a first lesion 272 may be seen on the
tissue region 270 in FIG. 13A with the lesion 272 as seen through
the hood 12 in the corresponding field of view 282. The location of
the first lesion 272 may accordingly be registered and illustrated,
e.g., on image 280 of display 278, as shown in FIG. 13B.
[0114] A directional movement indicator may be superimposed to
point in a first direction 284 on the monitor 278 to indicate a
direction in which the catheter hood 12 is moving (or is to be
moved) relative to the tissue surface 270 and/or other lesions.
Thus, FIG. 14A shows the position of a second lesion 274 which has
been formed (or is to be formed) on the tissue surface 270. Image
280 may illustrate the position of the second lesion 274 relative
to the first lesion 272 and the field of view 282 may show the
visual image of the lesion 274 itself, as shown in FIG. 14B. The
directional indicator may indicate a second direction 284' in which
the hood 12 is moving (or is to be moved) to reach the location of
the third lesion 276 which is either formed or to be formed.
Likewise, FIG. 15A shows the position of a third lesion 276
relative to the first 272 and second 274 lesions while image 280
may reflect the relative positioning on monitor 278. Third lesion
276 may be shown in the field of view 282 while the directional
indicator may point to yet another direction 284'' in which hood 12
may be moved for lesion visualization and/or formation, as shown in
FIG. 15B.
[0115] When providing real-time visual images for the purposes of
tissue diagnosis or treatment, it may be useful to overlay relevant
information to aid the physician during diagnosis and/or treatment.
One such example of an overlay is shown in the monitor 278 of FIG.
16 which illustratively shows the field of view 282 as seen through
hood 12 with lesion 290 previously or recently formed. Any number
of physiologic or treatment parameters may be overlaid directly
upon the monitor 278 for display to the user to facilitate
assessment or treatment, e.g., for estimating the depth of the
lesion formed. In this example, treatment information 292 (e.g.,
positional information, applied power levels, time of ablation
treatment, etc.) may be superimposed on the image of lesion 290.
Any other additional information 294 (e.g., applied voltage, tissue
thickness, etc.) may also be displayed upon monitor 278 for display
to the user.
[0116] Another overlay that may be applied is related to visually
representing the electric potential of the tissue surface.
Electrodes positioned along the hood may be used to measure the
electrical potential (such as the bipolar voltage amplitude or
monopolar voltage amplitude relative to a reference catheter or
Wilson central terminal) of points on a tissue surface. Further
examples of electrodes positioned along the hood and/or distal
membrane which may be utilized herein are described in detail in
U.S. patent application Ser. No. 12/118,439, which is incorporated
herein by reference above.
[0117] FIG. 17A shows a monitor view of measured gradient of
electric potential 300 of the tissue overlaid upon the visualized
tissue region seen in the field of view 282 through hood 12. An
electrical potential indication chart 302 may be seen also on
monitor 278 to indicate the level of detected electrical potential
for reference by the user. During lesion formation, as shown in
FIG. 17B, the measured electric potential at the region of the
lesion 304 may be monitored and overlaid atop the visualized
lesion. A threshold value of electrical potential may be optionally
preset by the user such that if the measured electrical potential
of the lesion is reduced during ablation, e.g., <0.5 mV bipolar
voltage, then an indicator may alert the user that the lesion has
been successfully electrically isolated from the surrounding
tissue. This may facilitate physician assessment as to when lesion
formation is complete.
[0118] Additionally and/or alternatively, other information may be
overlaid upon monitor 278 for facilitate physician assessment. For
example, FIG. 18A illustrates an example where the temperature
gradient 310 of the visualized tissue may be measured and
superimposed upon the visualized tissue utilizing temperature
sensors, as described in further detail in U.S. patent application
Ser. No. 12/118,439, which is incorporated herein by reference
above. A temperature indication chart 312 may be shown along the
monitor 278 for reference by the user. As previously described,
ablation may be controlled such that the tissue remains within
prescribed temperature limits. Overlaying the temperature
information of the lesion 314 as it is being formed may assist the
physician, e.g., in assessing whether to terminate the ablation
should a localized hot spot develop on the tissue surface, as shown
in FIG. 18B.
[0119] Yet another example of an informational overlay which may
facilitate tissue treatment assessment may incorporate the distance
of a tissue region to be treated (or undergoing treatment) to a
predetermined anatomical object or location. For example, ablation
of heart tissue typically occurs near the location of the
esophagus, which lies very close to and often touches the outer
wall of the left atrium, within the body. The heat from the
ablation procedure may penetrate through the tissue of the left
atrium and reach the esophagus. Uncontrolled ablation may thus
present a risk as lesions may be formed which extend towards or in
proximity to the esophagus thus potentially damaging the esophageal
tissue. Such damage is extremely dangerous as the damaged esophagus
may become infected and lead to an esophageal fistula (hole in the
esophagus). Over time, this may lead to an infection spreading into
the heart wall which carries a relatively high mortality rate. To
avoid damage to the esophagus (or any other object or anatomical
structure in proximity to the ablated tissue region), mapping
catheters and other imaging methods such as use of swallowed
contrast agents or probes to indicate either the pre-operative or
real-time position of the esophagus may be used. To that end, some
physicians have used standard mapping catheters to record the
pre-procedure location of the esophagus. However, such a
pre-procedure location determination fails to account for the
mobile nature of the esophagus. The esophagus generally does not
remain stationary. Rather, the esophagus often moves back and forth
thereby positioning itself in different locations relative to the
heart wall. As such, the esophagus may change its location during a
catheter-based endocardial procedure. The pre-procedure
determination fails to account for this movement. Accordingly,
displaying information in real-time such as the proximity of the
ablation catheter to the probe on the monitor 278 may facilitate
such treatments, as shown in FIG. 19, which shows lesion 320 and
distance information to a preselected object 322, such as the
esophagus. Moreover, a directional indicator to the object 324 may
also be imposed on monitor 278 to indicate to the user the relative
direction to the object.
[0120] Non-limiting examples of suitable analysis techniques for
determining distance for use with the system, devices, and methods
described herein may include impedance measurement, pacing signal
amplitude measurement, use of magnetic fields, use of Hall effect
sensors, inductance measurement, capacitance measurement, etc.
Thus, a physician may continuously monitor throughout an entire
mapping and/or ablation procedure the position of the object, such
as the esophagus, relative to the device in use in the heart. This
continuous, real time monitoring of the location of the esophagus
may further accounts for the movement of the esophagus to decrease
the risk of damage to the esophagus. Additional examples which may
be utilized herein are further described in detail in U.S. Pat.
Pub. 2007/0106287 A1, which is incorporated herein by reference in
its entirety.
[0121] It is also possible to overlay information relating to
particular metrics on the monitor 278 during visualization or
ablation. For example, FIG. 20 illustrates an example of how
distances 332 between two selected points may be measured directly
on the monitor 278 to provide metric information 330 such as the
length of a particular lesion. Such overlays may be utilized to
determine, e.g., the surface size of the lesion precisely to
facilitate physician assessment of lesion size. It may also be used
to accurately measure anatomical features in the body. Typically, a
reticule of a known distance may be included within the field of
view which would allow for calibration of the measurement to a know
distance. The accuracy of this measurement would be highest for
objects that are in the same plane as the calibration distance.
Further examples of measuring tissue regions in vivo which may be
used herein with the devices and methods are shown and described in
detail in U.S. Ser. No. 12/118,439 filed May 9, 2008, which is
incorporated herein by reference in its entirety.
[0122] Aside from measuring anatomical features, another feature
which physicians may utilize with the captured visual images of
tissue may also include the monitoring of changes in color of a
lesion formed over time. Tissue color may be used as a good
indicator of the stage of completion of the lesion forming process
as normal, unablated myocardial tissue is characteristically pink
or red in color. During ablation the lesion site will change color
due to heating, dessication, denaturation of proteins, and/or
ischemia. The lesion site will typically become white and then
possibly black, brown, or yellow as ablation continues if applied
beyond the usual limits. During real-time visualization and
ablation it may become difficult to distinguish the degree of color
change that has taken place due to the graduated nature of the
color change.
[0123] An example of monitoring color changes in tissue during
ablation treatment is illustrated in FIG. 21A, which shows an
overlay of multiple images of the tissue surface at preselected
time intervals as ablation progresses from, e.g., 10 secs to 60
secs. The time intervals at which the captured images may be
selected for viewing may be selected at relatively higher or lower
sampling rates. As shown in this example, images of lesion 320 may
be captured, e.g., at a recorded ablation time 340 of 10 sec, 30
sec, and 60 sec with a first corresponding image 342, second
corresponding image 344, and third corresponding image 346 showing
the progression of the tissue coloring from a pink or red state
eventually to a blanched condition. Having these images
simultaneously displayed may provide contextual information to the
user in determining whether sufficient ablation had' occurred in
the tissue being treated.
[0124] Another variation is shown in FIG. 21B which illustrates
monitor 278 showing a particular measured region 348 of lesion 320
tracked and imaged over a period of time from a first measured
ablation time 352 to a final measured ablation time 354, e.g., from
10 sec to 60 sec. A temperature chart 350 may be provided
illustrating the eventual change in tissue color as ablation
progresses through the ablation treatment. One or more indicators
may show the tissue coloring at a corresponding ablation time,
e.g., from a first corresponding tissue image 356 to a final
corresponding tissue image 358, which may be available to the user
for assessment.
[0125] In monitoring the blanching of the tissue being treated
during ablation, the degree of blanching may be determined by a
number of different methods. Blanching occurs as a result of
heating a tissue region which causes proteins to denature and
desiccate. This eliminates blood flow from the tissue hence turning
it from a pink or red color to a white color. Thus, blanching of
tissue may serve as a visual indicator of ablated tissue. One
example is shown in the flowchart 360 of FIG. 22 which illustrates
how certain tissue characteristics may be monitored. Once the
target tissue to be treated has been identified and the
visualization and treatment catheter securely apposed against the
tissue surface 362, ablation may be initiated 364 while under
direct visualization through hood 12. A processor in communication
with the imager may monitor a histogram of color channels of the
tissue being visualized 366 and the processor may then determine a
rate of change of the color histogram 368. If the rate of change is
determined by the processor to be higher than a preset limit, this
may be an indication that the tissue is blanching at a higher rate
than desired and the processor may continue to monitor the tissue
color change. Otherwise, if the rate of color change is lower than
the preset limit, then the processor may determine the degree of
surface reflectance 370. Again; if the processor indicates that the
surface reflectance is higher than a preset value, then the color
may continue to be monitored otherwise if the reflectance is lower
than the preset value, a determination may be made as to whether
there is any appearance of particular colors from the tissue which
may indicate that ablation of the tissue is nearing completion,
e.g., white, brown, yellow, black, etc. 372. If the processor does
detect the appearance of any of these particular colors, an audible
or visual indicator may notify the physician 374 and ablation may
be stopped automatically by the processor or directly by the
physician 376.
[0126] Additionally and/or alternatively, a processor may control
the flow of the purging fluid which may also be used to conduct a
current to the tissue to be treated. As illustrated in FIG. 23,
flowchart 380 shows an example where the color change of the lesion
may also be utilized for controlling or altering the purging fluid
flow through the hood and over the tissue region being visualized
and/or treated. It is generally desirable to deliver the lowest
amount of saline to the patient through the hood 12 as an excessive
flow of saline may cause the balance of electrolytes in the body to
fluctuate potentially resulting in hyponatremia. Thus, once the
hood 12 has been sufficiently apposed against the tissue surface,
e.g., by utilizing ultrasound 382 as described above or through
other methods, the saline fluid may be introduced into hood 12 to
begin purging of the blood within the hood and to clear the
visualization field 384. This fluid may be introduced at an initial
predetermined rate and registering of the RGB ratio of the imaged
underlying tissue may begin 386, as described above.
[0127] If the processor determines that the detected RGB color
channels are increasing at a desirable preset rate in approaching a
predefined boundary (utilizing parameters such as hue, saturation,
etc.) 388, then the percentage of the color red may be determined
for the captured image 392 and if the this percentage is above a
predetermined level, then this is an indication that the visual
field is sufficiently clearing of blood. However, if the RGB color
channels are determined not to be increasing at a desirable rate,
then the processor may automatically increase a flow rate 390 of
the saline into the hood 12 to increase the rate at which blood is
cleared. Likewise, if the percentage of the detected color red is
found to be below the predetermined level, then monitoring of the
color may be continued until the blood is sufficiently cleared from
the visual field of hood 12.
[0128] Once the percentage of the detected color red is at a
desired level, then the saline flow rate may be reduced to a
predetermined level 394, e.g., defined by the physician or active
recirculation of the saline may be produced within the hood. A
determination may then be made as to whether to maintain the flow
optimization 396 in which case if flow optimization is continued,
then the color change within the hood may be continued to be
monitored. Otherwise, the flow control may be terminated 398.
[0129] Yet another parameter utilizing the captured visual images
during tissue ablation may include the detection of bubbles during
ablation. The formation of bubbles may be visible on the monitor
near or at the edges of the visual field and these bubbles may be
generally indicative of high rates of heating, over-blanching of
tissue, or a potential steam popping. FIG. 24 illustrates a
flowchart 400 which shows one method for utilizing bubble detection
where the process may begin 402 by acquiring the visual image 404,
as previously described. The visual image may be processed by a
processor to find locations of any "hotspots" 406, i.e., areas of
high reflection, which may be indicative of the presence of
bubbles. The visual field may then be searched for potentially
spherical objects 408 and further monitored to determine whether a
radius or diameter of any spherical objects are growing 410 during
the ablation process. In the event that the detected radius is not
any larger than a preset limit 412, then the process of searching
may continue 414. Otherwise, if the radius is determined to exceed
the preset limit, then the bubble diameter may continue to be
monitored over time 416. The processor may then determine whether
the number of detected bubbles in the visual field exceed a
threshold value 418. In the event that the number of detected
bubbles are insufficient, the physician may be notified and/or the
power level may be maintained or increased 420 and the visual field
may be continued to be monitored for the formation of bubbles.
Otherwise, if the number of detected bubbles exceed the threshold
number, then an alert may notify the physician and/or the system
may power down automatically and/or the flow rate may be increased
to cool the tissue region down in temperature 422.
[0130] The system then alerts the physician to take a measure of
corrective actions which may include increasing the saline flow
rate or powering down the system among other things. Bubbles may be
difficult to detect with the naked eye, hence this protocol may be
useful in alerting physicians immediately upon the presence of even
tiny bubbles.
[0131] Additional methods and systems for bubble detection during
tissue treatment are further described in detail in U.S. patent
application Ser. No. 12/118,439 filed May 9, 2008, which has been
incorporated herein by reference above.
[0132] The various protocols or methods disclosed may be used in
any combination for processing the visual images generated.
Additionally the overlays disclosed may be used in any combination
as well to provide users with one or more layers of
information.
[0133] In yet another example for processing captured visual images
of tissue regions, FIGS. 25A and 25B illustrate side and plan views
of a hood 12 which is placed into contact against a tissue region T
to be visualized and/or treated. As the underlying tissue region
moves such as during a cardiac or respiratory cycle, hood 12 may be
inadvertently shifted from a first location 430 to a second
location 432 over the tissue surface, as indicated respectively by
two points labeled A and B. When such movement occurs, the region
being visualized may move continually making it difficult to
observe the tissue or to perform any procedures upon the tissue.
Such movement can be monitored visually by several methods such
that the user is able to determine an appropriate time to begin a
procedure. The overlap region 434 may be calculated between the
first location 430 and second location 432 compared against a
threshold limit. With the distance of hood movement known, a
procedure may be initiated and/or stopped appropriate each time the
hood 12 is expected to move such that treatment may be synchronized
according to hood and tissue movement.
[0134] In yet another example of utilizing the captured images,
FIGS. 26A and 26B show side and monitor views of a hood 12 which is
insufficiently apposed against the surface of a tissue region T to
be visualized and/or treated. As it may be difficult to determine
if the hood 12 is seated perpendicularly on the tissue surface or
is in an off-axis configuration, it may be possible to detect and
correct for such off-axis alignment from the tissue by processing
of the visual images. If hood 12 is not placed into direct
apposition against the tissue surface, gases introduced into hood
12 along with the purging fluid may form along the side of hood 12
which is not in contact with the tissue, i.e., bubbles 440 may form
along a gap or spacing 442 between hood 12 and the tissue surface.
These bubbles 440 may be visible in the field of view 282 and thus
alert the user that the hood 12 positioning along the tissue may
require readjustment.
[0135] The applications of the disclosed invention discussed above
are not limited to certain treatments or regions of the body, but
may include any number of other treatments and areas of the body.
Modification of the above-described methods and devices for
carrying out the invention, and variations of aspects of the
invention that are obvious to those of skill in the arts are
intended to be within the scope of this disclosure.
[0136] Moreover, various combinations of aspects between examples
are also contemplated and are considered to be within the scope of
this disclosure as well.
* * * * *